/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.method.annotation;

import java.util.LinkedHashMap;
import java.util.Map;

import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.ModelAndViewContainer;

/**
 * Resolves {@link Map} method arguments annotated with an @{@link RequestParam}
 * where the annotation does not specify a request parameter name.
 * See {@link RequestParamMethodArgumentResolver} for resolving {@link Map}
 * method arguments with a request parameter name.
 *
 * <p>The created {@link Map} contains all request parameter name/value pairs.
 * If the method parameter type is {@link MultiValueMap} instead, the created
 * map contains all request parameters and all there values for cases where
 * request parameters have multiple values.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @see RequestParamMethodArgumentResolver
 * @since 3.1
 */
public class RequestParamMapMethodArgumentResolver implements HandlerMethodArgumentResolver {

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        RequestParam requestParam = parameter.getParameterAnnotation(RequestParam.class);
        if (requestParam != null) {
            if (Map.class.isAssignableFrom(parameter.getParameterType())) {
                return !StringUtils.hasText(requestParam.name());
            }
        }
        return false;
    }

    @Override
    public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
            NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

        Class<?> paramType = parameter.getParameterType();

        Map<String, String[]> parameterMap = webRequest.getParameterMap();
        if (MultiValueMap.class.isAssignableFrom(paramType)) {
            MultiValueMap<String, String> result = new LinkedMultiValueMap<>(parameterMap.size());
            for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {
                for (String value : entry.getValue()) {
                    result.add(entry.getKey(), value);
                }
            }
            return result;
        } else {
            Map<String, String> result = new LinkedHashMap<>(parameterMap.size());
            for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {
                if (entry.getValue().length > 0) {
                    result.put(entry.getKey(), entry.getValue()[0]);
                }
            }
            return result;
        }
    }
}
